The present invention relates to an optical pickup for use in a disk player such as a DVD or a CD and a method of fixing a plate provided with an electronic component such as a photodiode. More particularly, the present invention concerns a technique whereby the fixation of the plate can be effected speedily and accurately.
Conventionally, a technique disclosed in the Unexamined Japanese Patent Application Publication No.Sho62-89249 and the like is known as a technique concerning an optical pickup. One of its examples will be described with reference to FIG. 5. In this optical pickup, a bilateral pair of projecting portions 1b are projectingly provided integrally on one end face 1a of a housing 1, and a plate 2 with a photodiode PD is fixed between the two projecting portions 1b. A collimator lens QWP and an objective lens OL are disposed on the other end face 1c side of the housing 1, a half mirror HM is disposed in an inclined state in a groove portion 3 of the housing 1, and a plate 4 with a semiconductor laser LD is fixed to a side surface 1d of the housing 1. Laser light is projected onto a disk D from the semiconductor laser LD through the half mirror HM, the collimator lens QWP, and the objective lens OL, and the light reflected therefrom is received by the photodiode PD through the half mirror HM, thereby reading information recorded in the disk D.
A description will be given of the procedure of fixing the plate 2 with the photodiode PD in the above-described arrangement. As shown by the phantom lines in FIG. 6, the plate 2 is attracted to a permanent magnet 6b (see FIG. 7A) provided on a lower surface of a distal end of a positioning arm 6, and is retained by a plurality of pins 6a provided projectingly on the lower surface of the distal end of the arm 6. As the positioning arm 6 is moved in three-dimensional directions a to f in the back-and-forth, left-and-right, and vertical directions, the plate 2 is positioned between the two projecting portions 1b with a predetermined interval xcex1 from the end face 1a of the housing 1, as shown in FIG. 7A, so as to align the center of the photodiode PD with the axis of the objective lens OL. Next, as shown in FIG. 7B, by means of an applicator 7 an adhesive 8 is applied to two gaps which are each formed between either side edge 21 of the plate 2 and the housing 1. The adhesive 8 is allowed to cure so as to fix the plate 2 to the housing 1, and the positioning arm 6 is raised to move the pins 6a away from the plate 2.
Conventionally, as the aforementioned adhesive 8, an ultraviolet curing adhesive is generally used, and the ultraviolet curing adhesive is applied over each entire range between either side edge 2a of the plate 2 and the housing 1, as shown in FIG. 7B.
With the above-described conventional arrangement, as the ultraviolet curing adhesive applied over each entire range between either side edge 2a of the plate 2 and the housing 1 is allowed to cure instantly by the application of ultraviolet rays thereto, there is an advantage that the plate 2 can be fixed to the housing 1 in a short time. However, since the degree of shrinkage of the ultraviolet curing adhesive due to temperature change is large, there is a possibility that the center of the photodiode PD becomes positionally offset from the axis of the objective lens OL.
Accordingly, it is conceivable to use as the adhesive 8 a thermosetting adhesive whose degree of shrinkage due to the temperature change is small, and to apply the thermosetting adhesive over each entire range between either side edge 2a of the plate 2 and the housing 1. With the thermosetting adhesive, however, since it takes time to heat and cure the hat curing adhesive, it is necessary to maintain the support of the plate 2 by the positioning arm 6 for a relatively long time, so that this method lacks mass productivity.
In view of the above-described conventional drawbacks, the object of the invention is to provide an optical pickup which makes it possible to speedily and accurately fix a plate provided with an electronic component such as a photodiode, as well as a method of fixing a plate with an electronic component.
To attain the above object, the invention according to aspect 1 is characterized in that a plate with a photodiode is positioned with a slight interval with respect to a housing, that a small amount of an ultraviolet curing adhesive is applied between either side edge of the plate and the housing, that the ultraviolet curing adhesive is allowed to cure by application of ultraviolet rays thereto to temporarily fix the plate to the housing, that an appropriate amount of a thermosetting adhesive is applied between a central portion of the either side edge of the plate and the housing, and that the thermosetting adhesive is allowed to cure by heating so as to finally fix the plate to the housing.
According to the above-described construction, since the plate with a photodiode is temporarily fixed to the housing by the ultraviolet curing adhesive, there is no need to support the plate at the time of final fixation by the thermosetting adhesive, so that it is possible to overcome the drawback of the thermosetting adhesive that it takes time to cure. In addition, since the amount of ultraviolet curing adhesive applied can be reduced by the portion by which the thermosetting adhesive is applied, it is possible to overcome the drawback of the ultraviolet curing adhesive that the degree of shrinkage due to the temperature change is large. Thus by the combination of the two adhesives, the drawbacks of the two adhesives can be overcome, and the fixation of the plate with the photodiode to the housing can be effected speedily and accurately.
Further, since the four corners of the plate can be temporarily fixed positively to the housing by the ultraviolet curing adhesive, and the thermosetting adhesive is applied between the cured ultraviolet curing adhesive portions, the efflux of the thermosetting adhesive to the outside can be reliably prevented, and the plate can be finally fixed firmly to the housing.
The invention according to aspect 2 is characterized in that a plate with a electronic component is positioned with a slight interval with respect to a housing, that a small amount of an ultraviolet curing adhesive is applied between the plate and the housing, that the ultraviolet curing adhesive is allowed to cure by application of ultraviolet rays thereto to temporarily fix the plate to the housing, that an appropriate amount of a thermosetting adhesive is applied between the plate and the housing, and that the thermosetting adhesive is allowed to cure by heating so as to finally fix the plate to the housing.
According to the above-described construction, since the plate with an electronic component is temporarily fixed to the housing by the ultraviolet curing adhesive, there is no need to support the plate at the time of final fixation by the thermosetting adhesive, so that it is possible to overcome the drawback of the thermosetting adhesive that it takes time to cure. In addition, since the amount of ultraviolet curing adhesive applied can be reduced by the portion by which the thermosetting adhesive is applied, it is possible to overcome the drawback of the ultraviolet curing adhesive that the degree of shrinkage due to the temperature change is large. Thus by the combination of the two adhesives, the drawbacks of the two adhesives can be overcome, and the fixation of the plate with the electronic component to the housing can be effected speedily and accurately.
The invention according to aspect 3 is characterized in that, in the optical pickup according to aspect 2, the ultraviolet curing adhesive is applied to a plurality of portions at predetermined intervals between either side edge of the plate and the housing, and that the thermosetting adhesive is applied to gaps other than portions where the ultraviolet curing adhesive has been applied between the either side edge of the plate and the housing.
According to the above-described construction, since a plurality of portions of either side edge of the plate are temporarily fixed firmly to the housing by the ultraviolet curing adhesive, the plate can be positively supported so as not to move unexpectedly while the thermosetting adhesive applied for final fixation is allowed to cure.
The invention according to aspect 4 is characterized in that, in the optical pickup according to aspect 2, the ultraviolet curing adhesive is applied a central portion of either side edge of the plate and the housing, and that the thermosetting adhesive is applied between each corner portion of the either side edge of the plate and the housing.
According to the above-described construction, since only the central portions of the side edges of the plate are temporarily fixed to the housing by the ultraviolet curing adhesive, and the amounts of the ultraviolet curing adhesive applied are very small, it is possible to reliably overcome the drawback peculiar to the ultraviolet curing adhesive that the degree of shrinkage due to the temperature change is large.
The invention according to aspect 5 is characterized by comprising the steps of: positioning a plate with an electric component at a predetermined interval from a housing as a positioning arm retaining the plate is moved in three-dimensional directions including back-and-forth, left-and-right, and vertical directions; applying a small amount of an ultraviolet curing adhesive between either side edge of the plate and the housing; allowing the ultraviolet curing adhesive to cure by application of ultraviolet rays thereto to temporarily fix the plate to the housing; moving the positioning arm from the plate; applying an appropriate amount of a thermosetting adhesive to gaps other than portions where the ultraviolet curing adhesive has been applied between the either side edge of the plate and the housing; and allowing the thermosetting adhesive to cure by heating so as to finally fix the plate to the housing.
According to the above-described construction, before the plate with the electronic component is finally fixed to the housing by the thermosetting adhesive, the plate is temporarily fixed by the ultraviolet curing adhesive in a state in which the plate is supported by the positioning arm. After the temporary fixation, the positioning arm can be immediately moved away from the plate, and it is unnecessary to maintain the support of the plate by the positioning arm until the curing of the thermosetting adhesive in a conventional manner, so that this arrangement excels in mass productivity. In addition, since the amount of the ultraviolet curing adhesive applied can be reduced by the portion by which the thermosetting adhesive is applied, it is possible to overcome the drawback of the ultraviolet curing adhesive that the degree of shrinkage due to the temperature change is large. Thus by the combination of the two adhesives, the drawbacks of the two adhesives can be overcome, and the fixation of the plate with the electronic component to the housing can be effected speedily and accurately.